Chiral Assembly and Recognition of Seven Copper (II) Coordination Polymers from Tartaric Acid Derivative Ligands

A pair of enantiomeric ligands, (2R,3R)-dibenzyl-2,3-bis(isonicotinoyloxy)succinate ((R,R)-L) and (2S,3S)-dibenzyl-2,3-bis(isonicotinoyloxy)succinate ((S,S)-L), are designed and synthesized. Seven copper (II) coordination polymers {[Cu((R,R)-L)Br₂ (THF)] ⋅ CH₃ CN} _n (1 a) and {[Cu((S,S)-L)Br₂ (THF)] ⋅ CH₃ CN}_n (1 b), {[Cu((R,R)-L)Cl₂ (THF)] ⋅ CH₃ CN}_n (2 a) and {[Cu((S,S)-L)Cl₂ (THF)] ⋅ CH₃ CN}_n (2 b), {[Cu((R,R)-L)(NO₃ )₂ (CH₃ CN)]}_n (3 a) and {[Cu((S,S)-L)(NO₃ )₂ (CH₃ CN)]}_n (3 b), {[Cu((R,R)-L)₂ (CH₃ CN)₂ ](ClO₄ )₂  ⋅ 3CH₃ CN}_n (4) were obtained through the assemblies with CuBr₂ , CuCl₂  ⋅ 2H₂ O, Cu(NO₃ )₂  ⋅ 3H₂ O, Cu(ClO₄ )₂  ⋅ 6H₂ O, respectively. Single-crystal X-ray diffraction and circular dichroism analysis demonstrate that 1 a-3 a, 1 b-3 b have a mono chiral one-dimensional (1D) chain-like spiral structure, while 4 have 1D chain-like structure whose metal centers have chiral propeller coordination environment. Ligand structure, anions and solvent systems have a regulatory effect on the formation of chiral helical structure. Further investigation has proved that 1 a can be used as circular dichroism spectrum probe for monitoring L-/D-cysteine and L-/D-penicillamine configuration and concentration in aqueous media based on ligand interchange mechanism.